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IAJPS, 2014, 1(1), 1-10. Mohammed Ishaq et.al

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ISSN 2349-7750

IINNDDOO AAMMEERRIICCAANN JJOOUURRNNAALL OOFF

PPHHAARRMMAACCEEUUTTIICCAALL SSCCIIEENNCCEESS

Available online at: http://www.iajps.com Research Article

FORMULATION AND EVALUATION OF BILAYER TABLET

CONTAINING METRONIDAZOLE AS AN IMMEDIATE

RELEASE LAYER AND NORFLOXACIN AS A SUSTAIN

RELEASE LAYER

E. Satheesh Kumar1, B. Mohammed Ishaq*

2, Shaik Muneer

2, Dr. V. Sreedhar

1,

Dr. Hindustan Abdul Ahad1, Dr. K. Vanitha Prakash

3

1. Department of Pharmaceutics, Balaji College of Pharmacy Rudrampeta bypass, Anantapur - 515001, India.

2. Department of Pharmaceutical Analysis, Balaji College of Pharmacy, Rudrampeta Bypass, Anantapur - 515001,

India.

3. Department of Pharmaceutical Analysis, SSJ College of Pharmacy, Gandipet, Hyderabad, India.

*Corresponding author:

B. Mohammed Ishaq

Email: [email protected]

ABSTRACT:

The aim of this work is to formulate Sustained bilayer tablets of Norfloxacin (NFX) and Metronidazole

(MET) by wet granulation by using different ratios of Xanthan gum and Carbopol. Metronidazole is a

synthetic antibacterial, anti-amoebic and anti protozoal agent. Norfloxacin used as antibacterial agent.

The Combination of MET with NFX is expected to be improving effectiveness of therapy in comparison

with individual drugs. Xanthan gum and Carbopol were selected because they were reported to give

sustained release and naturally occurring. The MET and NFX bi-layer sustained release tablets were

prepared by wet granulation method by using different polymers such as xanthan gum and carbopol as

sustained release polymers and along with Poly vinyl pyrrolidine K 30 (PVP K30) as binding agent. The

NFX Sustained release and MET immediate release was evaluated for morphological characteristic,

physical characteristic, chemical characteristic and stability. The results obtained were satisfactory and

within specified limits as per Pharmacopoeias. MET immediate layer released 98% to 99% within 2

hours. But NFX sustained layer 99.5% drug released up to 12 hours in F8 formulation. So, F8 was

showed good results compare to other formulations. Formulation F8 fulfills our objective of formulating

a bilayer tablet of sustained release of NFX and immediate release layer of MET.

Key words: Sustained bilayer tablets, Norfloxacin, Metronidazole, Xanthan gum, Carbopol.

http://www.iajps.com/

mailto:[email protected]


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INTRODUCTION:

In the recent times, bi-layer tablets are gaining importance in the design of oral controlled drug

delivery systems. Bi-layer tablets are novel drug delivery systems where combination of two or more

drugs in a single unit[1]. They are preferred for the following reasons: to co-administer two different

drugs in the same dosage form, to minimize physical and chemical incompatibilities, for staged drug

release, IR and SR in the same tablet, for chronic condition requiring repeated dosing. In the present study

a combination drug therapy is recommended for treatment of amoebiasis and other colonic infections to

allow medications of different mechanism of action to complement each other and together effectively

combat the microbes at lower than maximum doses of each[2,8]. The rational for combination therapy is

to encourage the use of lower doses of drug to minimize dose dependent side effects and adverse

reactions.

MET is a highly bitter drug, used in the treatment of intestinal protozoal infection like a

moebiasis, giardiasis, trichomonas vaginitis[3] etc. These drugs are to be delivered to the colon for their

effective action against E. histolytica wherein the trophozoites reside in the lumen of the caecum and

large intestine and adhere to the colonic mucus and epithelial layers. But the pharmacokinetic profile of

metronidazole indicates that the drug is completely and promptly absorbed after oral administration

reaching a concentration in plasma of about 10 µg/ml approximately 1 hr after a single 500 mg dose. The

administration of this drug in conventional tablet dosage form provides minimal amount of metronidazole

for local action in the colon, still resulting in the relief of amoebiasis, but with unwanted systemic effects

[4].

Norfloxacin, l-ethyl-6-fluoro-1,4-di-hydro-4-oxo-7-(1-piperazinyl)-3-quinoline carboxylic acid, is

a synthetic antibacterial fluoroquinolone [5]. Quinolones belongs to synthetic class of antimicrobial

agents with potent antimicrobial activity which are effective orally and parentally for a wide variety of

infectious diseases [6]. It is active on both actively dividing as well as dormant bacteria by inhibiting

bacterial DNA gyrase. It is effective in the treatment of urinary tract infections, gonococcal urethritis and

infectious diarrhea [7].

The objective of the study is to design and evaluate bilayer tablets of MET and NFX using

polymers such as Xanthan gum and Carbopol. And to carry out the Pre and post compressional

parameters for the powder blend of bilayered tablets as well as final finished dosage form.

MATERIALS AND METHODS:

Chemicals and Reagents: Table 1 shows the chemical/reagent and drugs and their source. And table 2 shows the source of

instruments used for this study.

Table 1: Source of chemicals and ingredients

S. No. Ingredients/chemicals/solvents Manufacturer /supplier

1 Norfloxacin Medrich Labs, Bangalore

2 Metronidazole Aurobindo Pharma, Hyderabad

3 Xanthan gum Colorcon Asia private limited

4 Carbopol Colorcon Asia private limited

5 PVP K30 BASF corporation

6 Iso propyl alcohol Qualigens fine chemicals

7 Stearic acid DMV- Fonterra excipients

8 Starch DMV- Fonterra excipients

9 Talc Signet chemical corporation pvt ltd

10 Di potassium hydrogen phosphate S.D. fine chemicals

All the chemicals were of AR grade.


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Table 2: Manufacturers of Instruments/Apparatus

S.NO INSTRUMENT/APPARATUS MANUFACTURER

1 Tablet pilot press, 9 stations Chamunda pharma pvt Ltd, Ahmedabad. (Model PP-1).

2 Friability test apparatus Singhala scientific industries, Ambala.

3 Monsanto hardness tester Singhala scientific industries, Ambala.

4 Dissolution test apparatus

(USP Type II),

Electro lab, Mumbai.(Model: TDT-08L)

5 UV Spectrophotometer Schimadzu

6 FTIR Schimadzu

7 Digital vernier caliper Absolute Digimate, industrial gin stores, Hyderabad

8 Digital balance LCGC Chromatographic solution, Hyderabad

9 pH Meter Singhala scientific industries, Ambala.

12 Glass wares --

Methods:

Formulation of tablets:

Sustained release Bilayer metronidazole and Norfloxacin tablets were prepared by wet

granulation method. Various batches were prepared by changing the ratio of Xanthan gum and Carbopol

to identify the most effective formulation. Norfloxacin and polymer mixture were prepared by

homogeneously mixing with Xanthan gum, Carbopol, Starch dried, PVP, Talc and Stearic acid in a glass

mortar for 15 minutes. The powder was screened through a 60 µm sieve to get uniform granules.

Simultaneously Metronidazole and polymer mixture were prepared by homogeneously mixing

with Starch (Dried) and PVP, Talc and Stearic acid in a glass mortar for 15 mins. The powder was dried

for 15 mins in hot air oven and screened through 60 µm sieve to get uniform granules. Metronidazole and

Norfloxacin granules were then compressed using an 8 mm diameter die in a 9-station rotary punching

machine (Ahmadabad, India). The upper punch was raised and the Metronidazole granules were

compressed, again Norfloxacin granules were placed on the 1st compressed metronidazole layer. The two

layers were then compressed into a bilayer tablet. Each tablet weighed 600 mg. Table 3 summarizes the

formulas to prepare bylayer immediate release metronidazole and sustain release Norfloxacin.

Table 3: Composition of immediate release layer of metronidazole and sustain release Norfloxacin

bylayer tablets

Formulation codes F1 F2 F3 F4 F5 F6 F7 F8 F9

I

N

G

R

E

D

I

E

N

T

S

Immediate Release layer (mg)

Metronidazole 250 250 250 250 250 250 250 250 250

Starch Dried 28 28 28 28 28 28 28 28 28

PVP 15 15 15 15 15 15 15 15 15

Stearic acid 5 5 5 5 5 5 5 5 5

Talc 2 2 2 2 2 2 2 2 2

Sustained Release layer (mg)

Norfloxacin 150 150 150 150 150 150 150 150 150

Xanthan gum 50 75 100 - - - 50 50 25

Carbopol - - - 50 75 100 25 50 50

Starch Dried 83 58 33 83 58 33 58 33 58

PVP 10 10 10 10 10 10 10 10 10

Stearic acid 5 5 5 5 5 5 5 5 5

Talc 2 2 2 2 2 2 2 2 2

IPA Q.S Q.S Q.S Q.S Q.S Q.S Q.S Q.S Q.S

Total Weight (mg) 600 600 600 600 600 600 600 600 600


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Evaluation of Granules Flow Properties [1, 8]: The prepared granules were evaluated for parameters like bulk density, taped density, Carr index,

Angle of repose, and Hausner’s ratio, loss on drying. The results are as in table 4 and 5.

Evaluation of tablets [1, 8]:

The prepared formulas were subjected to following tests:

Thickness

The thickness of the each tablet was measured by using vernier caliper and the average thickness

was calculated.

Weight variation

Formulated tablets were tested for weight uniformity, 20 Tablets were weighed collectively and

individually. From the collective weight, average weight was calculated. The percent weight variation

was calculated by using the following formula.

Hardness

The hardness of Tablets was measured by Monsanto hardness tester. The hardness was measured

in terms of kg/cm2.

Friability

The Roche friability test apparatus was used to determine the friability of the Tablets. Twenty

pre-weighed Tablets were placed in the apparatus and operated for 100 revolutions and then the Tablets

were reweighed. The percentage friability was calculated according to the following formula.

Drug Content

For drug content, the one tablet was crushed and transferred to 1000 ml volumetric flask and add

small quantity of acetic acid then make up to 1000 ml with pH 6.8 phosphate buffer. The solution was

filtered through Whatman filter paper (0.45µm pore size), Metronidazole and Norfloxacin were analyzed

at 320nm and 279nm respectively using double beam UV/Visible spectrophotometer after suitable

dilution. The content of drug was calculated from standard curve.

In-vitro drug release study

The USP type II rotating paddle method was used to study the drug release from the bilayer

tablet. The dissolution medium consisted of 900 ml of phosphate buffer pH 1.2 for two hours. The release

study was performed at 37 ± 0.50 C, with a rotation speed of 50 rpm. The disk was placed at the bottom

of the dissolution vessel. After that dissolution medium was changed to phosphate buffer pH 6.8 for a

period of 10 hrs. Aliquots (5ml each) were withdrawn at regular time intervals and replaced with fresh

medium to maintain sink conditions. The samples were filtered, with appropriate dilutions with phosphate

buffer pH 6.8 and Metronidazole and Norfloxacin were analyzed at 320nm and 279nm respectively using

double beam UV/Visible spectrophotometer after suitable dilution. The content of drug was calculated

from standard curve.

Stability studies:

The formulation F8 was selected and the stability studies were carried out at accelerated condition

of 40±2 0C, 75±5 % RH conditions, stored in desiccators, the tablets were packed in amber colour screw

cap container and kept in above said condition for period of three months. The tablets were analyzed

periodically for their physical appearance and in-vitro drug release.


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Kinetic Studies

The following plots were made: cumulative % drug release vs. time (zero order kinetic model);

log cumulative of % drug remaining vs. time (first order kinetic model); cumulative % drug release vs.

square root of time (higuchi model). The regression coefficient R2 value nearer to 1 indicates the model

best fits the release mechanism.

RESULTS AND DISCUSSION:

Drug excipient compatibility by FTIR Spectroscopy:

FTIR study demonstrates that no change in the individual peaks of MET and NFX and physical

mixture of both drugs. It showed that drugs have no incompatibility problem. FTIR spectras were

represented in Figure 1-4.

Figure 1: FTIR Spectrum of Norfloxacin

Figure 2: FTIR Spectrum of Metronidazole


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Figure 3: FTIR Spectrum of Norfloxacin with Polymer mixture

Figure 4: FTIR Spectrum of Metronidazole with Polymer mixture


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Evaluation of Granules:

The sustained release layer and immediate release layer granules were evaluated for bulk density,

tapped density, angle of repose, compressibility index, hausner’s ratio, loss on drying of the all

formulations i.e. F1 to F9. The results were found to be within the limits of standard specifications. The

granules were shows good flow properties. The results were tabulated in table 4 and 5.

Table no 4: Results of evaluation of immediate release layer granules

Formulations Bulk Density (gm/ml)

(Mean±SD)

Tapped Density

(gm/ml) (Mean±SD)

Carr’s index (%)

(Mean±SD)

Hausner ratio

(Mean±SD)

Angle of Repose (θ)

(Mean±SD)

F1 0.557 ± 0.0055 0.642 ± 0.0022 13.23 ± 0.16 1.15 ± 0.0044 29.53 ± 0.066

F2 0.548 ± 0.0036 0.632 ± 0.0021 13.29 ± 0.22 1.15 ± 0.0037 32.25 ± 0.023

F3 0.564 ± 0.0022 0.643 ± 0.0051 12.33 ± 0.89 1.14 ± 0.0029 30.23 ± 0.026

F4 0.561 ± 0.0057 0.647 ± 0.0028 13.29 ± 0.12 1.15 ± 0.0023 29.45 ± 0.057

F5 0.579 ± 0.0010 0.645 ± 0.0075 10.25 ± 0.6 1.11 ± 0.0024 31.47 ± 0.026

F6 0.580 ± 0.0022 0.658 ± 0.0011 11.85 ± 0.88 1.13 ±0.0084 30.40 ± 0.034

F7 0.542 ± 0.0010 0.629 ± 0.0023 13.83 ± 0.32 1.16 ± 0.001 33.26.00 ± 0.060

F8 0.544 ± 0.0089 0.618 ± 0.0098 11.97 ± 0.73 1.13 ± 0.0027 31.44 ± 0.026

F9 0.522 ± 0.0090 0.599 ± 0.0009 12.85 ± 0.29 1.14 ± 0.0020 34.27 ± 0.019

Table no 5: Results of evaluation of sustain release layer granules

Formulations Bulk Density

(gm/ml)(Mean±SD)

Tapped Density

(gm/ml)(Mean±SD)

Carr’s index

(%)(Mean±SD)

Hausner ratio

(Mean±SD)

Angle of Repose (θ)

(Mean±SD)

F1 0.557 ± 0.0055 0.642 ± 0.0022 08.75 ± 0.16 1.09±0.0044 29.00 ± 0.066

F2 0.548 ± 0.0036 0.678 ± 0.0021 09.65 ± 0.22 1.13±0.0037 27.00 ± 0.023

F3 0.574 ± 0.0022 0.633 ± 0.0051 07.33 ± 0.89 1.11±0.0029 26.00 ± 0.026

F4 0.601 ± 0.0057 0.657 ± 0.0028 08.98 ± 0.12 1.15±0.0023 28.00 ± 0.057

F5 0.599 ± 0.0010 0.645 ± 0.0075 11.75 ± 0.6 1.18±0.0024 29.00 ± 0.026

F6 0.600 ± 0.0022 0.698 ± 0.0011 13.89 ± 0.88 1.55±0.0084 28.00 ± 0.034

F7 0.512 ± 0.0010 0.599 ± 0.0023 12.64 ± 0.32 1.19 ± 0.001 29.00 ± 0.060

F8 0.644 ± 0.0089 0.693 ± 0.0098 15.98 ± 0.73 1.18±0.0027 27.00 ± 0.026

F9 0.522 ± 0.0090 0.599 ± 0.0009 13.89 ± 0.29 1.17±0.0020 28.00 ± 0.019

Evaluation of Tablets:

The prepared bi-layer sustained release tablets were evaluated for physico-chemical properties

like description, thickness, weight variation, hardness, friability, disintegration time for immediate layer,

drug content.

Description

The prepared bi-layer tablets were oval in shape, sustained released was in off white colour,

immediate released was in white colour.

Weight variation and Thickness

The weight variation of bi-layer tablets was found to be in the range of 591 ± 9.19 mg to 604 ±

5.32 mg and the thickness of bi-layer tablets was found to be in the range of 6.9 ± 0.02 to 7.0 ± 0.04 mm

for all the formulations (F1 TO F9). The results were tabulated in table 6.


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Hardness and friability

Hardness was affecting the release of drug from formulations. The hardness of bi-layer tablets

was found to be in the range of 5.1 ± 0.31 kp to 6.3 ± 0.52 kp and friability of bi-layer tablets was found

in the range of 0.34 ± 0.025% to 0.74 ± 0.043% for all the formulations (F1 TO F9). The results were

tabulated in table 6.

Drug content

Drug content of bi-layer tablets was estimated by assay using UV spectrophotometer. The amount

of metronidazole was found to be in the range of 98.99% to 101.45% and the amount of norfloxacin was

found to be in the range of 98.76 % to 101.3 % for all the formulations (F1 - F9). The results were

tabulated in table 6.

Table no 6: Results of Physiochemical properties of bilayer tablets

Formulation

Code

Thickness

(mm) SD

Weight

Variation

(mg) SD

Hardness

(Kg/cm2)

SD

Friability

(%) SD

Drug Content(%)

Metronidazole Norfloxacin

F1 6.9 ± 0.03 601 ± 8.55 5.7 ± 0.15 0.34 ± 0.025 99.89 100.4

F2 7.0 ± 0.01 595 ± 7.94 5.6 ± 0.25 0.42 ± 0.03 101.45 98.90

F3 6.9 ± 0.02 593 ± 9.81 5.1 ± 0.31 0.35 ± 0.042 99.32 99.56

F4 7.0 ± 0.02 604 ± 5.32 5.3 ± 0.21 0.43 ± 0.036 100.25 99.23

F5 7.0 ± 0.03 591 ± 9.19 6.1 ± 0.24 0.52 ± 0.023 98.99 101.3

F6 7.0 ± 0.04 594 ± 5.9 5.9 ± 0.45 0.63 ± 0.053 99.78 98.98

F7 6.9 ± 0.05 599 ± 6.3 6.3 ± 0.52 0.48 ± 0.06 100.5 99.45

F8 7.0 ± 0.04 602 ± 4.9 5.4 ± 0.63 0.59 ± 0.07 99.86 100.6

F9 6.9 ± 0.06 596 ± 6.8 5.7 ± 0.74 0.74 ± 0.043 101.3 98.76

In vitro Dissolution Study

Based on the in-vitro release profile Metronidazole immediate layer released 98% to 99% within

2 hours. But Norfloxacin sustained layer 99.5% drug released up to 12 hours in F8 formulation. So, F8

was showed good results compare to other formulations. This was achieved by increasing the polymer

concentration by combining two polymers such as which release the drug in a controlled rate at regular

time intervals in appropriate concentrations as per the limits. Hence formulation F8 was selected for

further stability studies. Invitro drug release patterns were shown in figure 5.


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Figure 5: In Vitro % of Drug Release of formulations F1-F9.

Stability Study

The stability studies of formulation F8 were carried out at accelerated condition of 40±2 ºC, 75±5

% RH conditions. The tablets were withdrawn at every one month and evaluate the tablet parameters like

Appearance, drug content and in-vitro drug release at end of 3rd

month. There is no change in physical

parameters and the drug content was reduced but it is within the standard specifications .There is no

significant change in the In-vitro drug release. The results were tabulated in table 7. According to three

months data, the shelf of stability sample (F8) was calculated.

Table 7: Stability data of Bilayer tablets (F8)

Parameters INITIAL 1st month 2nd month 3rd month

Physical appearance White round

shape No Change No Change No change

Drug content (%) Metronidazole 100.5 99.4 98.35 98.05

Norfloxacin 99.9 98.6 97.8 97.8

Drug release (%) Metronidazole 99.2 98.4 97.5 96.5

Norfloxacin 99.5 98.6 96.8 96.5

CONCLUSION:

The Metronidazole and Norfloxacin bi-layer sustained release tablets were prepared by wet

granulation method by using different polymers such as xanthan gum and carbopol as sustained release

polymers and along with Poly vinyl pyrrolidine K 30 (PVP K30) as binding agent. The Norfloxacin

Sustained release and Metronidazole immediate release was evaluated for morphological characteristic,

physical characteristic, chemical characteristic and stability. The results obtained were satisfactory and

within specified limits as per Pharmacopoeias

Metronidazole immediate layer released 98% to 99% within 2hours. But Norfloxacin sustained layer

99.5% drug released up to 12 hours in F8 formulation. So, F8 was showed good results compare to other

0

20

40

60

80

100

120

0 2 4 6 8 10 12 14

% O

F D

RU

G R

EL

EA

SE

TIME (HOURS)

IN VITRO % OF DRUG RELEASE FORMULATION F1-F9

F1 SR F1 IR F2 SR F2 IR F3 SR F3 IR




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formulations. Formulation F8 fulfills our objective of formulating a bilayer tablet of sustained release of

Norfloxacin and immediate release layer of Metronidazole.

ACKNOWLEDGEMENTS

The authors wish to thank Medrich Labs, Bangalore and Aurobindo Pharma, Hyderabad, India for

providing the gift samples of Norfloxacin and Metronidazole respectively.

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6. Murakawa GJ and Sable D, Quinolones in Dermatology, Clinical Dermatol, 21(1), 2003, 56-63.

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Pharm, 5, 1991, 681-94

8. Remington,“The Science and Practicen of pharmacy”, 20th Edition, 2005 Volume I, Pg.No.903-

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